1CPS::Governor(3)      User Contributed Perl Documentation     CPS::Governor(3)
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NAME

6       "CPS::Governor" - control the iteration of the "CPS" functions
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DESCRIPTION

9       Objects based on this abstract class are used by the "gk*" variants of
10       the CPS functions, to control their behavior. These objects are
11       expected to provide a method, "again", which the functions will use to
12       re-invoke iterations of loops, and so on. By providing a different
13       implementation of this method, governor objects can provide such
14       behaviours as rate-limiting, asynchronisation or parallelism, and
15       integration with event-based IO frameworks.
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CONSTRUCTOR

18   $gov = CPS::Governor->new
19       Must be called on a subclass which implements the "again" method.
20       Returns a new instance of a governor object in that class.
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SUBCLASS METHODS

23       Because this is an abstract class, instances of it can only be
24       constructed on a subclass which implements the following methods:
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26   $gov->again( $code, @args )
27       Execute the function given in the "CODE" reference $code, passing in
28       the arguments @args. If this is going to be executed immediately, it
29       should be invoked using a tail-call directly by the "again" method, so
30       that the stack does not grow arbitrarily. This can be achieved by, for
31       example:
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33        @_ = @args;
34        goto &$code;
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36       Alternatively, the Sub::Call::Tail may be used to apply syntactic
37       sugar, allowing you to write instead:
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39        use Sub::Call::Tail;
40        ...
41        tail $code->( @args );
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EXAMPLES

44   A Governor With A Time Delay
45       Consider the following subclass, which implements a "CPS::Governor"
46       subclass that calls "sleep()" between every invocation.
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48        package Governor::Sleep
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50        use base qw( CPS::Governor );
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52        sub new
53        {
54           my $class = shift;
55           my ( $delay ) = @_;
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57           my $self = $class->SUPER::new;
58           $self->{delay} = $delay;
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60           return $self;
61        }
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63        sub again
64        {
65           my $self = shift;
66           my $code = shift;
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68           sleep $self->{delay};
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70           # @args are still in @_
71           goto &$code;
72        }
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SEE ALSO

75       ·   Sub::Call::Tail - Tail calls for subroutines and methods
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AUTHOR

78       Paul Evans <leonerd@leonerd.org.uk>
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82perl v5.30.0                      2019-07-26                  CPS::Governor(3)